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The Atomic Bombings Reconsidered

Fifty years ago, during a three-day period in August 1945, the United States dropped two atomic bombs on Japan, killing more than 115,000 people and possibly as many as 250,000, and injuring at least another 100,000. In the aftermath of the war, the bombings raised both ethical and historical questions about why and how they were used. Would they have been used on Germany? Why were cities targeted so that so many civilians would be killed? Were there likely alternative ways to end the war speedily and avoid the Allies’ scheduled November 1, 1945, invasion of Kyushu?

Such questions often fail to recognize that, before Hiroshima and Nagasaki, the use of the A-bomb did not raise profound moral issues for policymakers. The weapon was conceived in a race with Germany, and it undoubtedly would have been used against Germany had the bomb been ready much sooner. During the war, the target shifted to Japan. And during World War II’s brutal course, civilians in cities had already become targets. The grim Axis bombing record is well known. Masses of noncombatants were also intentionally killed in the later stages of the American air war against Germany; that tactic was developed further in 1945 with the firebombing of Japanese cities. Such mass bombing constituted a transformation of morality, repudiating President Franklin D. Roosevelt’s prewar pleas that the warring nations avoid bombing cities to spare civilian lives. Thus, by 1945, American leaders were not seeking to avoid the use of the A-bomb on Japan. But the evidence from current archival research shows that by pursuing alternative tactics instead, they probably could still have obviated the dreaded invasion and ended the war by November.

Shifting from Germany to Japan

IN 1941, urged by emigre and American scientists, President Roosevelt initiated the atomic bomb project—soon code-named the Manhattan Project—amid what was believed to be a desperate race with Hitler’s Germany for the bomb. At the beginning, Roosevelt and his chief aides assumed that the A-bomb was a legitimate weapon that would be used first against Nazi Germany. They also decided that the bomb project should be kept secret from the Soviet Union, even after the Soviets became a wartime ally, because the bomb might well give the United States future leverage against the Soviets.

By mid-1944, the landscape of the war had changed. Roosevelt and his top advisers knew that the likely target would now be Japan, for the war with Germany would undoubtedly end well before the A-bomb was expected to be ready, around the spring of 1945. In a secret September 1944 memorandum at Hyde Park, Roosevelt and British Prime Minister Winston Churchill ratified the shift from Germany to Japan. Their phrasing suggested that, for the moment anyway, they might have had some slight doubts about actually using the bomb, for they agreed that “it might perhaps, after mature consideration, be used against the Japanese” (my emphasis).

Four days later, mulling over matters aloud with a visiting British diplomat and chief U.S. science adviser Vannevar Bush, Roosevelt briefly wondered whether the A-bomb should be dropped on Japan or whether it should be demonstrated in America, presumably with Japanese observers, and then used as a threat. His speculative notion seemed so unimportant and so contrary to the project’s long-standing operating assumptions that Bush actually forgot about it when he prepared a memo of the meeting. He only recalled the president’s remarks a day later and then added a brief paragraph to another memorandum.

Put in context alongside the dominant assumption that the bomb would be used against the enemy, the significance of F.D.R.’s occasional doubts is precisely that they were so occasional—expressed twice in almost four years. All of F.D.R.’s advisers who knew about the bomb always unquestioningly assumed that it would be used. Indeed, their memoranda frequently spoke of “after it is used” or “when it is used,” and never “if it is used.” By about mid-1944, most had comfortably concluded that the target would be Japan.

The bomb’s assumed legitimacy as a war weapon was ratified bureaucratically in September 1944 when General Leslie Groves, the director of the Manhattan Project, had the air force create a special group—the 509th Composite Group with 1,750 men—to begin practicing to drop atomic bombs. So dominant was the assumption that the bomb would be used against Japan that only one high-ranking Washington official, Undersecretary of War Robert Patterson, even questioned this notion after V-E Day. He wondered whether the defeat of Germany on May 8, 1945, might alter the plans for dropping the bomb on Japan. It would not.

The Assumption of Use

The Manhattan Project, costing nearly $2 billion, had been kept secret from most cabinet members and nearly all of Congress. Secretary of War Henry L. Stimson, a trusted Republican, and General George C. Marshall, the equally respected army chief of staff, disclosed the project to only a few congressional leaders. They smuggled the necessary appropriations into the War Department budget without the knowledge—much less the scrutiny—of most congressmen, including most members of the key appropriations committees. A conception of the national interest agreed upon by a few men from the executive and legislative branches had revised the normal appropriations process.

In March 1944, when a Democratic senator heading a special investigating committee wanted to pry into this expensive project, Stimson peevishly described him in his diary as “a nuisance and pretty untrustworthy…He talks smoothly but acts meanly.” That man was Senator Harry S Truman. Marshall persuaded him not to investigate the project, and thus Truman did not learn any more than that it involved a new weapon until he was suddenly thrust into the presidency on April 12, 1945.

In early 1945, James F. Byrnes, then F.D.R.’s “assistant president” for domestic affairs and a savvy Democratic politician, began to suspect that the Manhattan Project was a boondoggle. “If [it] proves a failure,” he warned Roosevelt, “it will be subjected to relentless investigation and criticism.” Byrnes’ doubts were soon overcome by Stimson and Marshall. A secret War Department report, with some hyperbole, summarized the situation “If the project succeeds, there won’t be any investigation. If it doesn’t, they won’t investigate anything else.”

Had Roosevelt lived, such lurking political pressures might have powerfully confirmed his intention to use the weapon on the enemy—an assumption he had already made. How else could he have justified spending roughly $2 billion, diverting scarce materials from other war enterprises that might have been even more useful, and bypassing Congress? In a nation still unprepared to trust scientists, the Manhattan Project could have seemed a gigantic waste if its value were not dramatically demonstrated by the use of the atomic bomb.

Truman, inheriting the project and trusting both Marshall and Stimson, would be even more vulnerable to such political pressures. And, like F.D.R., the new president easily assumed that the bomb should and would be used. Truman never questioned that assumption. Bureaucratic developments set in motion before he entered the White House reinforced his belief. And his aides, many inherited from the Roosevelt administration, shared the same faith.

Picking Targets

Groves, eager to retain control of the atomic project, received Marshall’s permission in early spring 1945 to select targets for the new weapon. Groves and his associates had long recognized that they were considering a weapon of a new magnitude, possibly equivalent to the “normal bombs carried by [at least] 2,500 bombers.” And they had come to assume that the A-bomb would be detonated well above ground, relying primarily on blast effect to do material damage, [so that even with] minimum probable efficiency, there will be the maximum number of structures (dwellings and factories) damaged beyond repair.”

On April 27, the Target Committee, composed of Groves, army air force men like General Lauris Norstad, and scientists including the great mathematician John Von Neumann, met for the first time to discuss how and where in Japan to drop the bomb. They did not want to risk wasting the precious weapon, and decided that it must be dropped visually and not by radar, despite the poor weather conditions in Japan during the summer, when the bomb would be ready.

Good targets were not plentiful. The air force, they knew, “was systematically bombing out the following cities with the prime purpose…of not leaving one stone lying on another: Tokyo, Yokohama, Nagoya, Osaka, Kyoto, Kobe, Yawata, and Nagasaki…The air force is operating primarily to laying [sic] waste all the main Japanese cities…Their existing procedure is to bomb the hell out of Tokyo.”

By early 1945, World War II—especially in the Pacific—had become virtually total war. The firebombing of Dresden had helped set a precedent for the U.S. air force, supported by the American people, to intentionally kill mass numbers of Japanese citizens. The earlier moral insistence on noncombatant immunity crumbled during the savage war. In Tokyo, during March 9-10, a U.S. air attack killed about 80,000 Japanese civilians. American B-29s dropped napalm on the city’s heavily populated areas to produce uncontrollable firestorms. It may even have been easier to conduct this new warfare outside Europe and against Japan because its people seemed like “yellow subhumans” to many rank-and-file American citizens and many of their leaders.

In this new moral context, with mass killings of an enemy’s civilians even seeming desirable, the committee agreed to choose “large urban areas of not less than three miles in diameter existing in the larger populated areas” as A-bomb targets. The April 27 discussion focused on four cities: Hiroshima, which, as “the largest untouched target not on the 21st Bomber Command priority list,” warranted serious consideration; Yawata, known for its steel industry; Yokohama; and Tokyo, “a possibility [though] now practically all bombed and burned out and…practically rubble with only the palace grounds left standing.” They decided that other areas warranted more consideration: Tokyo Bay, Kawasaki, Yokohoma, Nagoya, Osaka, Kobe, Kyoto, Hiroshima, Kure, Yawata, Kokura, Shimonoseki, Yamaguchi, Kumamoto, Fukuoka, Nagasaki, and Sasebo.

The choice of targets would depend partly on how the bomb would do its deadly work—the balance of blast, heat, and radiation. At their second set of meetings, during May 11-12, physicist J. Robert Oppenheimer, director of the Los Alamos laboratory, stressed that the bomb material itself was lethal enough for perhaps a billion deadly doses and that the weapon would give off lethal radioactivity. The bomb, set to explode in the air, would deposit “a large fraction of either the initial active material or the radioactive products in the immediate vicinity of the target; but the radiation…will, of course, have an effect on exposed personnel in the target area.” It was unclear, he acknowledged, what would happen to most of the radioactive material: it could stay for hours as a cloud above the place of detonation or, if the bomb exploded during rain or in high humidity and thus caused rain, “most of the active material will be brought down in the vicinity of the target area.” Oppenheimer’s report left unclear whether a substantial proportion or only a small fraction of the population might die from radiation. So far as the skimpy records reveal, no member of the Target Committee chose to dwell on this matter. They probably assumed that the bomb blast would claim most of its victims before the radiation could do its deadly work.

In considering targets, they discussed the possibility of bombing the emperor’s palace in Tokyo and “agreed that we should not recommend it but that any action for this bombing should come from authorities on military policy.” They decided to gather information on the effectiveness of using the bomb on the palace.

The Target Committee selected their four top targets: Kyoto, Hiroshima, Yokohama, and Kokura Arsenal, with the implication that Niigata, a city farther away from the air force 509th group’s Tinian base, might be held in reserve as a fifth. Kyoto, the ancient former capital and shrine city, with a population of about a million, was the most attractive target to the committee. “From the psychological point of view,” the committee minutes note, “there is the advantage that Kyoto is an intellectual center for Japan and [thus] the people there are more apt to appreciate the significance of such a weapon.” The implication was that those in Kyoto who survived the A-bombing and saw the horror would be believed elsewhere in Japan.

Of central importance, the group stressed that the bomb should be used as a terror weapon—to produce “the greatest psychological effect against Japan” and to make the world, and the U.S.S.R. in particular, aware that America possessed this new power. The death and destruction would not only intimidate the surviving Japanese into pushing for surrender, but, as a bonus, cow other nations, notably the Soviet Union. In short, America could speed the ending of the war and by the same act help shape the postwar world.

By the committee’s third meeting, two weeks later, on May 28, they had pinned down matters. They chose as their targets (in order) Kyoto, Hiroshima, and Niigata, and decided to aim for the center of each city. They agreed that aiming for industrial areas would be a mistake because such targets were small, spread on the cities’ fringes, and quite dispersed. They also knew that bombing was imprecise enough that the bomb might easily miss its mark by a fifth of a mile, and they wanted to be sure that the weapon would show its power and not be wasted.

The committee understood that the three target cities would be removed from the air force’s regular target list, reserving them for the A-bomb. But, the members were informed, “with the current and prospective rate of…bombings, it is expected to complete strategic bombing of Japan by 1 Jan. 46 so availability of future [A-bomb] targets will be a problem.” In short, Japan was being bombed out.

The Ratification of Terror Bombing

On May 28, 1945, physicist Arthur H. Compton, a Nobel laureate and member of a special scientific panel advising the high-level Interim Committee newly appointed to recommend policy about the bomb, raised profound moral and political questions about how the atomic bomb would be used. “It introduces the question of mass slaughter, really for the first time in history,” he wrote. “It carries with it the question of possible radioactive poison over the area bombed. Essentially, the question of the use…of the new weapon carries much more serious implications than the introduction of poison gas.”

Compton’s concern received some independent support from General Marshall, who told Secretary Stimson on May 29 that the A-bomb should first be used not but against against civilians military installations—perhaps a naval base—and then possibly against large manufacturing areas after the civilians had received ample warnings to flee. Marshall feared “the opprobrium which might follow from an ill considered employment of such force.” A graduate of Virginia Military Institute and a trained soldier, Marshall struggled to retain the older code of not intentionally killing civilians. The concerns of Compton the scientist and Marshall the general, their values so rooted in an earlier conception of war that sought to spare noncombatants, soon gave way to the sense of exigency, the desire to use the bomb on people, and the unwillingness or inability of anyone near the top in Washington to plead forcefully for maintaining this older morality.

On May 31, 1945, the Interim Committee, composed of Stimson, Bush, Harvard President James Conant, physicist and educator Karl T. Compton, Secretary of State designate James F. Byrnes, and a few other notables, discussed the A-bomb. Opening this meeting, Stimson, the aged secretary of war who had agonized over the recent shift toward mass bombing of civilians, described the atomic bomb as representing “a new relationship of man to the universe. This discovery might be compared to the discoveries of the Copernican theory and the laws of gravity, but far more important than these in its effects on the lives of men.”

Meeting, as they were, some six weeks before the first nuclear test at Alamogordo, they were still unsure of the power of this new weapon. Oppenheimer told the group that it would have an explosive force of between 2,000 and 20,000 tons of TNT. Its visual effect would be tremendous. “It would be accompanied by a brilliant luminescence which would rise to a height of 10,000 to 20,000 feet,” Oppenheimer reported. “The neutron effect [radiation] would be dangerous to life for a radius of at least two-thirds of a mile.” He estimated that 20,000 Japanese would be killed.

According to the committee minutes, the group discussed “various types of targets and the effects to be produced.” Stimson “expressed the conclusion, on which there was general agreement, that we could not give the Japanese any warning; that we could not concentrate on a civilian area; but that we should seek to make a profound psychological impression on as many of the inhabitants as possible. At the suggestion of Dr. Conant, the secretary agreed that the most desirable target would be a vital war plant employing a large number of workers and closely surrounded by workers’ houses.”

Directed by Stimson, the committee was actually endorsing terror bombing—but somewhat uneasily. They would not focus exclusively on a military target (the older morality), as Marshall had recently proposed, nor fully on civilians (the emerging morality). They managed to achieve their purpose—terror bombing—without bluntly acknowledging it to themselves. All knew that families—women, children, and, even in the daytime, during the bomb attack, some workers—dwelled in “workers’ houses.”

At the committee’s morning or afternoon session, or at lunch, or possibly at all three times—different members later presented differing recollections—the notion of a noncombat demonstration of the A-bomb came up. The issue of how to use the bomb was not even on Stimson’s agenda, nor was it part of the formal mandate of the Interim Committee, but he may have showed passing interest in the subject of a noncombat demonstration. They soon rejected it. It was deemed too risky for various reasons: the bomb might not work, the Japanese air force might interfere with the bomber, the A-bomb might not adequately impress the Japanese militarists, or the bomb might incinerate any Allied POWs whom the Japanese might place in the area.

The discussion on May 31 had focused substantially on how to use the bomb against Japan. At one point some of the members had considered trying several A-bomb strikes at the same time and presumably on the same city. Groves opposed this notion, partly on the grounds that “the effect would not be sufficiently distinct from our regular air force bombing program.” Like the others, he was counting on the dramatic effect of a single bomb, delivered by a single plane, killing many thousands. It was not new for the air force to kill so many Japanese, but this method would be new. And the use of the new weapon would carry, as stressed by American proclamations in early August, the likelihood of more nuclear attacks on Japanese cities—a continuing “rain of ruin.”

Two weeks after the Interim Committee meeting, on June 16, after emigre physicists James Franck and Leo Szilard and some colleagues from the Manhattan Project’s Chicago laboratory raised moral and political questions about the surprise use of the bomb on Japan, a special four-member scientific advisory committee disposed of the matter of a noncombat demonstration. The group was composed of physicists Arthur Compton, J. Robert Oppenheimer, Enrico Fermi, and Ernest O. Lawrence. By one report, Lawrence was the last of the four to give up hope for a noncombat demonstration. Oppenheimer, who spoke on the issue in 1954 and was not then controverted by the other three men, recalled that the subject of a noncombat demonstration was not the most important matter dealt with during the group’s busy weekend meeting and thus did not receive much attention. On June 16, the four scientists concluded: “We can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use.”

At that time, as some members of the scientific panel later grudgingly acknowledged, they knew little about the situation in Japan, the power of the militarists there, the timid efforts by the peace forces there to move toward a settlement, the date of the likely American invasion of Kyushu, and the power of the still untested A-bomb. “We didn’t know beans about the military situation,” Oppenheimer later remarked pungently.

But even different counsel by the scientific advisers probably could not have reversed the course of events. The bomb had been devised to be used, the project cost about $2 billion, and Truman and Byrnes, the president’s key political aide, had no desire to avoid its use. Nor did Stimson. They even had additional reasons for wanting to use it: the bomb might also intimidate the Soviets and render them tractable in the postwar period.

Stimson emphasized this theme in a secret memorandum to Truman on April 25: “If the problem of the proper use of this weapon can be solved, we should then have the opportunity to bring the world into a pattern in which the peace of the world and our civilization can be saved.” Concern about the bomb and its relationship to the Soviet Union dominated Stimson’s thinking in the spring and summer of 1945. And Truman and Byrnes, perhaps partly under Stimson’s tutelage, came to stress the same hopes for the bomb.

The Agonies of Killing Civilians

During 1945, Stimson found himself presiding, with agony, over an air force that killed hundreds of thousands of Japanese civilians. Usually, he preferred not to face these ugly facts, but sought refuge in the notion that the air force was actually engaged in precision bombing and that somehow this precision bombing was going awry. Caught between an older morality that opposed the intentional killing of noncombatants and a newer one that stressed virtually total war, Stimson could neither fully face the facts nor fully escape them. He was not a hypocrite but a man trapped in ambivalence.

Stimson discussed the problem with Truman on June 6. Stimson stressed that he was worried about the air force’s mass bombing, but that it was hard to restrict it. In his diary, Stimson recorded: “I told him I was anxious about this feature of the war for two reasons: first, because I did not want to have the United States get the reputation of outdoing Hitler in atrocities; and second, I was a little fearful that before we could get ready the air force might have Japan so thoroughly bombed out that the new weapon would not have a fair background to show its strength.” According to Stimson, Truman “laughed and said he understood.”

Unable to reestablish the old morality and wanting the benefits for America of the new, Stimson proved decisive—even obdurate—on a comparatively small matter: removing Kyoto from Groves’ target list of cities. It was not that Stimson was trying to save Kyoto’s citizens; rather, he was seeking to save its relics, lest the Japanese become embittered and later side with the Soviets. As Stimson explained in his diary entry of July 24: “The bitterness which would be caused by such a wanton act might make it impossible during the long post-war period to reconcile the Japanese to us in that area rather than to the Russians. It might thus…be the means of preventing what our policy demanded, namely, a sympathetic Japan to the United States in case there should be any aggression by Russia in Manchuria.”

Truman, backing Stimson on this matter, insisted privately that the A-bombs would be used only on military targets. Apparently the president wished not to recognize the inevitable—that a weapon of such great power would necessarily kill many civilians. At Potsdam on July 25, Truman received glowing reports of the vast destruction achieved by the Alamogordo blast and lavishly recorded the details in his diary: a crater of 1,200 feet in diameter, a steel tower destroyed a half mile away, men knocked over six miles away. “We have discovered,” he wrote in his diary, “the most terrible bomb in the history of the world. It may be the fire destruction prophesied.” But when he approved the final list of A-bomb targets, with Nagasaki and Kokura substituted for Kyoto, he could write in his diary, “I have told Sec. of War…Stimson to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless, and fanatic…[t]he target will be a purely military one.” Truman may have been engaging in self-deception to make the mass deaths of civilians acceptable.

Neither Hiroshima nor Nagasaki was a “purely military” target, but the official press releases, cast well before the atomic bombings, glided over this matter. Hiroshima, for example, was described simply as “an important Japanese army base.” The press releases were drafted by men who knew that those cities had been chosen partly to dramatize the killing of noncombatants.

On August 10, the day after the Nagasaki bombing, when Truman realized the magnitude of the mass killing and the Japanese offered a conditional surrender requiring continuation of the emperor, the president told his cabinet that he did not want to kill any more women and children. Rejecting demands to drop more atomic bombs on Japan, he hoped not to use them again. After two atomic bombings, the horror of mass death had forcefully hit the president, and he was willing to return partway to the older morality—civilians might be protected from A-bombs. But he continued to sanction the heavy conventional bombing of Japan’s cities, with the deadly toll that napalm, incendiaries, and other bombs produced. Between August 10 and August 14—the war’s last day, on which about 1,000 American planes bombed Japanese cities, some delivering their deadly cargo after Japan announced its surrender—the United States probably killed more than 15,000 Japanese.

The Roads Not Taken

Before August 10, Truman and his associates had not sought to avoid the use of the atomic bomb. As a result, they had easily dismissed the possibility of a noncombat demonstration. Indeed, the post-Hiroshima pleas of Japan’s military leaders for a final glorious battle suggest that such a demonstration probably would not have produced a speedy surrender. And American leaders also did not pursue other alternatives: modifying their unconditional surrender demand by guaranteeing the maintenance of the emperor, awaiting the Soviet entry into the war, or simply pursuing heavy conventional bombing of the cities amid the strangling naval blockade.

Truman and Byrnes did not believe that a modification of the unconditional surrender formula would produce a speedy surrender. They thought that guaranteeing to maintain the emperor would prompt an angry backlash from Americans who regarded Hirohito as a war criminal, and feared that this concession might embolden the Japanese militarists to expect more concessions and thus prolong the war. As a result, the president and his secretary of state easily rejected Stimson’s pleas for a guarantee of the emperor.

Similarly, most American leaders did not believe that the Soviet entry into the Pacific war would make a decisive difference and greatly speed Japan’s surrender. Generally, they believed that the U.S.S.R.’s entry would help end the war—ideally, before the massive invasion of Kyushu. They anticipated Moscow’s intervention in mid-August, but the Soviets moved up their schedule to August 8, probably because of the Hiroshima bombing, and the Soviet entry did play an important role in producing Japan’s surrender on August 14. Soviet entry without the A-bomb might have produced Japan’s surrender before November.

The American aim was to avoid, if possible, the November 1 invasion, which would involve about 767,000 troops, at a possible cost of 31,000 casualties in the first 30 days and a total estimated American death toll of about 25,000. And American leaders certainly wanted to avoid the second part of the invasion plan, an assault on the Tokyo plain, scheduled for around March 1, 1946, with an estimated 15,000-21,000 more Americans dead. In the spring and summer of 1945, no American leader believed—as some later falsely claimed—that they planned to use the A-bomb to save half a million Americans. But, given the patriotic calculus of the time, there was no hesitation about using A-bombs to kill many Japanese in order to save the 25,000-46,000 Americans who might otherwise have died in the invasions. Put bluntly, Japanese life—including civilian life—was cheap, and some American leaders, like many rank-and-file citizens, may well have savored the prospect of punishing the Japanese with the A-bomb.

Truman, Byrnes, and the other leaders did not have to be reminded of the danger of a political backlash in America if they did not use the bomb and the invasions became necessary. Even if they had wished to avoid its use—and they did not—the fear of later public outrage spurred by the weeping parents and loved ones of dead American boys might well have forced American leaders to drop the A-bomb on Japan.

No one in official Washington expected that one or two atomic bombs would end the war quickly. They expected to use at least a third, and probably more. And until the day after Nagasaki, there had never been in their thinking a choice between atomic bombs and conventional bombs, but a selection of both—using mass bombing to compel surrender. Atomic bombs and conventional bombs were viewed as supplements to, not substitutes for, one another. Heavy conventional bombing of Japan’s cities would probably have killed hundreds of thousands in the next few months, and might have produced the desired surrender before November 1.

Taken together, some of these alternatives—promising to retain the Japanese monarchy, awaiting the Soviets’ entry, and even more conventional bombing—very probably could have ended the war before the dreaded invasion. Still, the evidence—to borrow a phrase from F.D.R.—is somewhat “iffy,” and no one who looks at the intransigence of the Japanese militarists should have fill confidence in those other strategies. But we may well regret that these alternatives were not pursued and that there was not an effort to avoid the use of the first A-bomb—and certainly the second.

Whatever one thinks about the necessity of the first A-bomb, the second—dropped on Nagasaki on August 9—was almost certainly unnecessary. It was used because the original order directed the air force to drop bombs “as made ready” and, even after the Hiroshima bombing, no one in Washington anticipated an imminent Japanese surrender. Evidence now available about developments in the Japanese government—most notably the emperor’s then-secret decision shortly before the Nagasaki bombing to seek peace—makes it clear that the second bomb could undoubtedly have been avoided. At least 35,000 Japanese and possibly almost twice that number, as well as several thousand Koreans, died unnecessarily in Nagasaki.

Administration leaders did not seek to avoid the use of the A-bomb. They even believed that its military use might produce a powerful bonus: the intimidation of the Soviets, rendering them, as Byrnes said, “more manageable,” especially in Eastern Europe. Although that was not the dominant purpose for using the weapon, it certainly was a strong confirming one. Had Truman and his associates, like the dissenting scientists at Chicago, foreseen that the A-bombing of Japan would make the Soviets intransigent rather than tractable, perhaps American leaders would have questioned their decision. But precisely because American leaders expected that the bombings would also compel the Soviet Union to loosen its policy in Eastern Europe, there was no incentive to question their intention to use the atomic bomb. Even if they had, the decision would probably have been the same. In a powerful sense, the atomic bombings represented the implementation of an assumption—one that Truman comfortably inherited from Roosevelt. Hiroshima was an easy decision for Truman.

The Redefinition of Morality

Only years later, as government archives opened, wartime hatreds faded, and sensibilities changed, would Americans begin seriously to question whether the atomic bombings were necessary, desirable, and moral. Building on the postwar memoirs of Admiral William Leahy and General Dwight D. Eisenhower, among others, doubts began to emerge about the use of the atomic bombs against Japan. As the years passed, Americans learned that the bombs, according to high-level American military estimates in June and July 1945, probably could not have saved a half million American lives in the invasions, as Truman sometimes contended after Nagasaki, but would have saved fewer than 50,000. Americans also came slowly to recognize the barbarity of World War II, especially the mass killings by bombing civilians. It was that redefinition of morality that made Hiroshima and Nagasaki possible and ushered in the atomic age in a frightening way.

That redefinition of morality was a product of World War II, which included such barbarities as Germany’s systematic murder of six million Jews and Japan’s rape of Nanking. While the worst atrocities were perpetrated by the Axis, all the major nation-states sliced away at the moral code—often to the applause of their leaders and citizens alike. By 1945 there were few moral restraints left in what had become virtually a total war. Even F.D.R.’s prewar concern for sparing enemy civilians had fallen by the wayside. In that new moral climate, any nation that had the A-bomb would probably have used it against enemy peoples. British leaders as well as Joseph Stalin endorsed the act. Germany’s and Japan’s leaders surely would have used it against cities. America was not morally unique—just technologically exceptional. Only it had the bomb, and so only it used it.

To understand this historical context does not require that American citizens or others should approve of it. But it does require that they recognize that pre- and post-Hiroshima dissent was rare in 1945. Indeed, few then asked why the United States used the atomic bomb on Japan. But had the bomb not been used, many more, including numerous outraged American citizens, would have bitterly asked that question of the Truman administration.

In 1945, most Americans shared the feelings that Truman privately expressed a few days after the Hiroshima and Nagasaki bombings when he justified the weapons’ use in a letter to the Federal Council of Churches of Christ. “I was greatly disturbed over the unwarranted attack by the Japanese on Pearl Harbor and their murder of our prisoners of war,” the president wrote. “The only language they seem to understand is the one we have been using to bombard them. When you have to deal with a beast you have to treat him as a beast.”